This invention relates to apparatus for mixing particulate material in a liquid. In the past, particulate material and liquids were mixed together in a common vessel by means of a mechanical agitator within the vessel which stirred the mixture until it reached the desired degree of uniformity, at which time the mixture was removed from the vessel and a new charge of liquid and particulate material were introduced therein. However, this procedure is time consuming and has to be carried out in batches rather than continuously. Also, some dry particulate materials are very difficult to wet. The dry particles tend to agglomerate with each other, and the liquid contacts the outside of the agglomeration, but does not penetrate to wet the inner particles. When mixed in tanks by mechanical agitators, a long time is needed to break up these agglomerations and wet all particles.
Centrifugal mixers have been proposed in the past in which particulate material falls upon a rotating cone and is flung by centrifugal force against a film of liquid that is moving downward under the force of gravity over a stationary cone that surrounds the rotating cone. The mixture of liquid and particulate material is then passed through a rotary mixing disc having intermeshed teeth which shear the mixture and increase its uniformity. This type of mixer permits continuous mixing but is still limited as regards uniformity of mixture with particulate material that tends to agglomerate and has the additional drawback that the feed rate is determined by a gravity feed of the liquid down a cone of fixed slope and thus the feed rate cannot be conveniently adjusted without changing the thickness of the film.